An electronic component, an electronic equipment, etc. are provided with an optical member (such as an optical film, an optical lens or a sealing material of a light emitting diode) in some cases.
As the optical member, it is required to use a resin material in some cases, for the following reason (i):
(i) Along with e.g. downsizing, higher integration and higher performance of e.g. an electronic component or an electronic equipment, an optical member is also required to be downsized. As a material for the optical member, a resin material is suitable with a view to readily processing the optical member into a small size.
Further, the optical member is required to have the heat resistance and the light resistance in some cases, for the following reasons (ii) and (iii):
(ii) An optical member is mounted on a circuit board by a solder reflow method in some cases. In the solder reflow method, it is desired to use a lead-free solder in order to cope with environmental problems. Accordingly, an optical member is required to have the heat resistance as to maintain a shape without being melted even at a reflow temperature (about 260° C.) of a lead-free solder.
(iii) Along with a tendency to high brightness of a light-emitting diode, a sealing material is required to have higher heat resistance and light resistance.
As a resin material excellent in the heat resistance and the light resistance, an ethylene/tetrafluoroethylene copolymer (hereinafter, referred to as ETFE) is known. However, a usual ETFE is not suitable for a resin material for optical members since the transparency is low due to high crystallinity.
As an ETFE having improved transparency, the following ETFE has been proposed.
ETFE comprising units (A) based on tetrafluoroethylene (hereinafter, referred to as TFE), units (B) based on ethylene (hereinafter, referred to as E) and units (C) based on CH2═CHCnF2n+1 (wherein n is an integer of from 2 to 10), wherein the molar ratio ((A)/(B)) of the above units (A) to the above units (B) is from 50/50 to 60/40, and the content of the units (C) is from 2 to 7 mol % (Patent Document 1).